1. Field of the Invention
The present invention relates to a substrate processing apparatus and an analysis method therefor, and more particularly, to a substrate processing apparatus for using gas to analyze a state in the apparatus.
2. Description of the Related Art
A substrate processing apparatus for performing plasma processing on substrates such as semiconductor wafers comprises a housing chamber (hereinafter referred to as the “chamber”) for housing a substrate, and performs the plasma processing on the substrate using a plasma generated in the chamber. In order to carry out proper plasma processing on the substrate, it is important to detect a state in the chamber or an end point of the plasma processing.
To detect the state in the chamber or the end point of plasma processing, there is known a method in which a window of quartz glass is fitted into a side wall of the chamber, a plasma spectroanalyzer is disposed such as to face the window, and spectral analysis is performed on plasma emission in the chamber by the spectroanalyzer (see, for example, paragraph [0038] of Japanese Laid-open Patent Publication No. 2004-319961).
However, with elapse of time, the window of the chamber can become clouded. Furthermore, a light receiving sensor provided in the spectroanalyzer must be replaced after passage of predetermined hours of use, and there is sometimes an individual difference in light-receiving performance between the sensor before replacement and the sensor after replacement. The cloud on the window in the chamber and the sensor replacement affect on a result of the spectral analysis by the spectroanalyzer.
Replacement of an inter-chamber part (i.e., a part disposed in the chamber) such as, for example, a sealed ring or a focus ring, can sometimes cause a difference in the state of plasma emission between before and after the replacement, even if recipe (processing condition) is kept unchanged between before and after the replacement. Thus, the plasma emission can be affected by the replacement of the inter-chamber part. In other words, a result of spectral analysis by a spectroanalyzer reflects the influence of the inter-chamber part replacement.
As described above, the result of spectral analysis by the spectroanalyzer does not simply reflect the state in the chamber, but also reflects other variation factors (such as influences of the cloud on the window of the chamber, the sensor replacement, and the inter-chamber part replacement). As a result, the state in the chamber cannot be detected with accuracy.